1. Field of the Invention
The field of the inventions as recited in the claims attached hereto is a subsea oil and gas well, and more particularly a system that allows angular alignment-free assembly of well components when completing the oil and gas well.
2. Discussion of Prior Art
A typical subsea oil or gas well includes a wellhead installed at the sea floor. The wellhead supports many components that are used to first drill the well and then remove oil or gas through the well. For example, a drilling blowout preventer (BOP) stack is installed on the wellhead, and a well bore is drilled while successively installing concentric casing strings in the well bore. Typically, each successive casing string is cemented at its lower end and includes a casing hanger sealed with a mechanical seal assembly at its upper end in the wellhead.
To produce a cased well, a production tubing string and tubing hanger are run into the well bore through the BOP stack and the tubing hanger is landed, sealed and locked in the wellhead. Then the BOP stack is removed and a Christmas tree is lowered onto the wellhead. A Christmas tree is an oilfield term for an assembly, installed at the top of the wellhead, that contains control valves and chokes to allow control of the flow of oil and gas from the subsea well. To ensure proper operation and safety of the well, connections are remotely formed between the Christmas tree, the wellhead, and the tubing hanger.
In a completed well system, the Christmas tree is connected to the top of the wellhead over the tubing hanger. The tubing hanger supports at least one production tubing string which extends into the well bore. The tubing hanger includes a production bore that communicates with the tubing string. The tubing hanger supports an annulus conduit that communicates with the annulus which surrounds the outside of the tubing string that is inside the innermost or production casing string. In addition, the tubing hanger includes at least one vertical annulus bore for communicating fluid between the annulus conduit and a corresponding annulus bore in the Christmas tree. The tubing hanger may additionally include one or more service and control conduits for communicating control fluids and well chemicals though the tubing hanger or electrical power to devices or positions located in or below the tubing hanger.
The tubing hanger normally is sealed and rigidly locked into the wellhead housing or component in which it is landed. The tubing hanger typically includes an integral locking mechanism which, when activated, secures the tubing hanger to the wellhead housing or a profile in the casing hanger. The locking mechanism ensures that any subsequent pressure from within the well acting on the tubing hanger will not cause the tubing hanger to lift from the wellhead.
Current oil and gas well completion systems require angular orientation of the tubing hanger with the wellhead and with the BOP stack and Christmas tree. In some completion systems, hydraulically remotely actuated pins or rods in the BOP stack are extended into the well bore to orient the tubing hanger or running tool during the completion process. This is done to orientate the tubing hanger to allow vertical stabs for the electrical connector to spatially line up in the vertical and horizontal planes so as to accomplish the tubing hanger interface. This arrangement requires very precise alignment tolerance due to the tolerance stack up variance in the vertical and horizontal planes as well as the machine tolerances in the equipment. Such alignment tolerance requires BOP stack modifications and “as build jigs” fabricated prior to running the tubing hanger and Christmas tree.
Furthermore, special tools for the tubing hanger are required prior to deployment. These tools and jigs must be maintained for well workover and abandonment of the well in order to properly align the associated BOP stack for subsequent employment. In a tubing spool or horizontal tree configuration, angular orientation is accomplished with a sleeve as part of the tubing spool or horizontal tree body. In the tubing spool this allows a vertical stab via a pin, because orientation is accomplished by a fixed orientation bushing. In the horizontal tree, electrical connection is accomplished via a mechanically or hydraulically actuated pin extended through the spool body into the tubing hanger where the electrical female part of the connection resides. Orientation again is accomplished due to the fixed orientation sleeve.
In some completion systems, orientation is accomplished using a bushing set by the drill string in the wellhead and oriented via a slot in the BOP wellhead connector. This arrangement requires that the BOP connector be oriented prior to running the BOP stack on the wellhead. The electrical connector is still made up with an oriented vertical stab.
The costs associated with such completion systems which require angular orientation are high. Such costs are described here.
The engineering work to set up and implement an orientation system into a BOP is significant. It requires two engineers at a cost of $200 per/hr. totaling about $16,000 and two man days of work.
The cost to modify a BOP stack for orientation during the drilling process requires temporary abandonment of the well. Such cost could be as high as $600,000 per day. For a five-day period, the total cost could be $3,000,000.
The cost of additional tool rentals to orientate tubing hangers is about $20,000.
For a horizontal completion, in order to orientate the functions of production bore, annulus bore, hydraulic feed through coupled with a concentric electrical connector, a helix on the tubing hanger sleeve is used to interface with a pin in the horizontal tree spool body. This procedure also requires temporary abandonment of the well, because the procedure can not be employed during the drilling of the well, and because the casing hangers require a full bore to the wellhead housing. As described above, temporary abandonment of a well costs about $600,000 per/day.
3. Identification of Objects of the Invention
The inventions as embodied in the claims attached hereto have as an object, a system that allows completion of an oil or gas well without any requirement for angular alignment of well components.
Another object is to provide a method for angular alignment-free completion of an oil or gas well.